The present invention relates to a method and apparatus for preparing containers of culture medium in isolation from an ambient atmosphere.
It is common clinical practice in identifying disease or the like, to grow a culture of bacteria removed from a patient. This is generally accomplished by inoculating a culture medium, such as an agar, with a sample of the bacteria of interest. The culture medium is contained within a petri dish or other container designed to hold the same for the growth of bacteria.
It is necessary for reliable results that the culture medium be free both of other bacteria which might grow and of any other contaminant which may either affect bacteria growth or make the results unreliable. That is, it is important that one know reliably that the bacteria which grows is a replication of the inoculated bacteria, and that there are no other contaminants within, on, or surrounding the culture medium which might adversely affect the growth of the bacteria of interest.
Petri dishes and other containers of culture medium are commonly prepared in the clinical laboratory in the ambient atmosphere. That is, the agar or other culture medium is placed in the dishes in the atmosphere prevailing in the laboratory. The culture medium often is provided in a dehydrated form and it is rehydrated at the time it is placed in the growth containers. Once filled, the petri dishes are generally transferred to protective chambers until such time as the medium is to be inoculated. It will be recognized that there is a chance the culture medium will be contaminated at the time it is rehydrated and placed in the the petri dishes. This problem is particularly acute with culture medium to be used to grow anaerobic bacteria, i.e., bacteria whose growth is inhibited by the presence of oxygen. The ambient atmosphere of a clinical laboratory will include oxygen, of course, and the rehydration of the medium and placement of the same in a petri dish in such atmosphere can result in oxygen contamination. There have been suggestions that this possibility can be obviated by rehydrating the media and placing it in containers in an isolated environment. In fact, small numbers of containers have been prepared in this way. However, it has not been practical until this time to prepare a large number of containers this way on a commercial basis. One problem is that humidity build-up in isolated environments often will cause deposition of water on the culture medium. The presence of water on a medium can materially affect its ability to sustain bacterial growth. Another problem is that until now there has not been a practical way to fill the containers continuously in an isolated environment. In this connection, glove box chambers have been proposed to be used. However, it typically requires a significant period of time to purge a glove box chamber of ambient atmosphere, and if the glove box chamber must be opened either to insert empty petri dishes or to remove filled ones, the purging cycle must be undergone before another batch of petri dishes can be filled.
Filled petri dishes and other containers are individually packaged and now provided commercially. However, because of the difficulties mentioned above, the dishes are neither prepared in an isolated, e.g., oxygen-free, environment nor packaged in a manner in which isolation is assured for a practical length of time.